Minamoto no Tametomo

During the Hogen Rebellion, he fought alongside his father in the siege of Shirakawa-den on the side of the defenders. Among the opponents were Taira no Kiyomori and his brother Yoshitomo. After the palace was set on fire by the enemy and could no longer be held, Tametomo was forced to flee. He was exiled to the island of Oshima, one of the Izu Islands.

In the Ryukyu Islands, it was long believed that he eventually reached Okinawa and founded the Chūzan Kingdom there by fathering the first king, Shunten. Although this version is highly improbable, it was recorded in the Chūzan Seikan of Shō Shōken, the first history of Ryukyu, and was probably passed down with the purpose of strengthening the mythological and ideological ties between Japan and Ryukyu.

Tametomo is known in the epic chronicles as an excellent archer. He is said to have sunk an entire Taira ship by piercing it below the waterline with a single arrow.

In 1170, as the conflict between the Minamoto and Taira dynasties continued, Tametomo was trapped on a small island by Taira warriors. He became possibly the first warrior in recorded history to commit seppuku.

Source: Wikipedia